public class Pillar {
      Geometry bottom;	//bottom是用抽象类Geometry声明的对象
      double height;
      Pillar (Geometry bottom,double height) {
		this.bottom = bottom;
		this.height = height;
      }
      public double getVolume() {
	  if (bottom==null) {
	     System.out.println("没有底，无法计算体积");
	     return  -1;			   	     }										
         return bottom.getAre()*height;							
     }

}
